The Role of Snow and Ice
in the Climate System
and
Global snow and ice cover (the
"cryosphere") plays a major role in global climate and hydrology
through a range of complex interactions and feedbacks, the best known of which
is the ice - albedo feedback. Snow and ice cover undergo marked seasonal
and long term changes in extent and thickness. The perennial elements -
the major ice sheets and permafrost - play a role in present-day regional and
local climate and hydrology, but the large seasonal variations in snow cover
and sea ice are of importance on continental to hemispheric scales. The
characteristics of these variations, especially in the Northern Hemisphere, and
evidence for recent trends in snow and ice extent are discussed.